CHANGES IN BODY SIZE AND PHYSICAL CHARACTERISTICS OF SOUTH AFRICAN UNDER-20 RUGBY UNION PLAYERS OVER A 13-YEAR PERIOD WAYNE P. LOMBARD,1,2 JUSTIN J. DURANDT,1 HERMAN MASIMLA,3 MERVIN GREEN,3 MICHAEL I. LAMBERT2
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Sports Science Institute of South Africa, Discovery High Performance Center; 2Department of Human Biology, Exercise Science and Sports Medicine, Faculty of Health Sciences, University of Cape Town; and 3South African Rugby Union ABSTRACT
INTRODUCTION
Lombard, WP, Durandt, JJ, Masimla, H, Green, M, and Lambert, MI. Changes in body size and physical characteristics of South African under-20 rugby union players over a 13-year period. J Strength Cond Res 29(4): 980–988, 2015—This study compared changes in the body size and physical characteristics of South African under-20 rugby union players over a 13-year period. A total of 453 South African under-20 players (forwards: n = 256 and backs: n = 197) underwent measurements of body mass, stature, muscular strength, endurance, and 10- and 40-m sprint times. A 2-way analysis of variance was used to determine significant differences for the main effects of position (forwards vs. backs) and time (1998–2010). The pooled data showed that forwards were significantly heavier (22%), taller (5%), and stronger (18%) than the backs. However, when 1 repetition maximum strength scores were adjusted for body mass, backs were stronger per kg body mass. Stature did not change over the 13-year period for both groups. There were, however, significant increases in muscular strength (50%), body mass (20%), and muscular endurance (50%). Furthermore, an improvement in sprint times over 40 (4%) and 10 m (7%) was evident over the period of the study. In conclusion, the players became heavier, stronger, taller, and improved their upperbody muscular endurance over the 13 years of the study. Furthermore, sprint times over 10 and 40 m improved over the same time period despite the increase in body mass. It can be speculated that the changes in physical characteristics of the players over time are possibly a consequence of (a) adaptations to the changing demands of the game and (b) advancements in training methods.
KEY WORDS forwards, backs, physiological testing
Address correspondence to Wayne P. Lombard, [email protected]. 29(4)/980–988 Journal of Strength and Conditioning Research Ó 2015 National Strength and Conditioning Association
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ugby union is an intermittent high-intensity collision sport, contested between 2 teams of 15 players. There are 8 forward players (forwards) and 7 backline players (backs) in each team. The forwards, whose key responsibility is gaining possession of the ball, are generally taller and heavier than the backs (8,12). However, the backs are usually faster than the forwards and are responsible for gaining field possession and scoring points (7,28). The playing time is 80 minutes (2 halves of 40 minutes), with the time of the ball in play ranging from 35 to 45 minutes, and the rest of the time made up of stoppages (21). Modern day athletes in general are bigger, stronger, and faster, especially at the elite level compared with athletes of 20 years ago (29). This can be attributed to a refinement of training techniques (1,26), nutrition (1,18), and in some cases ergogenic aids (17,18,26). In rugby union, the average size of players has steadily increased from 1905 with the rate of change from 1975 to 1999 being almost 3–4 times greater than the rate of change between 1905 and 1974 (26). This may also have something to do with the changing demands of the game, which have occurred as a result of certain rule changes (9). The number of collisions between players during a match has also increased (35). Between 1995 and 2004, the ball-in-play time increased by nearly 6 minutes in Bledisloe Cup matches, and the number of rucks increased from an average of 72–178 (28). It can be argued that these rule changes have affected the physical demands of the game. It is for this reason that recent research has tried to identify the physiological demands of the modern game. For example, a study using global positioning system tracking software provided insight into the various stresses placed on different positions (7). The study showed backs spent 42% of playing time at 80–90% of maximum heart rate (HRmax), whereas forwards spent approximately 27% of playing time in this heart rate zone. The study also showed that players generally only sprinted for a maximum of 4–6 seconds at any given time, covering distances of anywhere between 30 and 60 m (7). One of the key findings of the study was the actual
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Journal of Strength and Conditioning Research number of collisions experienced by the forwards (1,274 collisions) vs. backs (798 collisions) during a match (7). About 15% of the tackles of the backs and 25% of the forwards were rated as “moderate-heavy” to “severe” (7). Another study of provincial professional players used video analysis to show that forwards were involved in 68% of the total collisions (35). Therefore, it is generally accepted that the backline players are faster, whereas the forwards have more contact and as a result are generally the bigger and stronger players to ensure that they can handle these collisions. Physiological profiling of players has become ever increasingly important to determine their readiness to withstand the demands of a high-intensity contact sport (23). Furthermore, it has been shown that there is a direct relationship between specific physical characteristics and game statistics (e.g., sprint times vs. line breaks) in rugby union (31). For example, it was shown that the bigger teams are generally the more successful teams that compete in the Rugby World Cup (29). It has been well documented that strength, power, and upper-body muscular endurance are important characteristics of modern era rugby players, allowing them to be more fatigue resistant and stronger in the tackle and ball carrying situations (2,9). With this in mind, it is plausible to assume that in the modern era of professional rugby, players who are generally bigger, faster, stronger, and can resist fatigue tend to have an advantage over smaller, less powerful, and less fit opponents (31). Indeed, at all the previous world cup tournaments, the team performing best had the tallest backs and heaviest forwards (30). Therefore, to perform at a high level and be able to cope with the physicality of the modern game, players need to train to become stronger, bigger, and faster, while being able to resist the fatigue arising from short duration high intensity activity. It is obviously also important for the players to have a high level of skill for the demands of a specific position, but it is increasingly difficult for players without these physical characteristics to successfully compete at the highest levels, even if they have the prerequisite skills. There are a lack of studies on the body size and physical characteristics of junior rugby players (under 20 years) competing at the international level. These data are important because about 32% of players who play for the South African under-20 team progress to play for the senior national team when they mature (27). Therefore, it is important to have reference data for young rugby players so that they can be adequately prepared for competition at a senior level. Moreover, quantifying how these measurements have evolved over time provides an insight into which measurements are particularly important for success. Therefore, the aim of this study was to compare changes in the body size and physical characteristics of South Africa’s National under-20 rugby union players (forwards and backs) over a 13-year period from 1998 to 2010. This period spans an era starting just after the onset of professionalism of the game to the modern era where the influence of professionalism has filtered down to junior (under-20) levels.
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METHODS Experimental Approach to the Problem
The study is a retrospective descriptive study using a repeated cross-sectional design conducted over 13 years, in which the body size and physical characteristics of under-20 rugby players were measured. Subjects
Each player completed a preparticipation screening questionnaire and an informed consent form before testing. All under 18 players had parental consent prior to participating. Players who had contraindications to testing were excluded from that particular test if necessary. The population sample consisted of under-20 rugby players who represented the junior South African National team between 1998 and 2010 (n = 453). The Human Research Ethics Committee of the University of Cape Town approved the study (HREC REF 001/2011). The group was divided into 2: forwards (n = 256) and backs (n = 197). The mean age of the players was 18.1 6 0.7 years at the time of testing. Players were tested in either December or January of 1998–2010 before the finalization of the squad before the junior world championships of that year. The championships were held in different parts of the world between the months of June and July (20). Testing Protocol
The testing protocol consisted of an evaluation of the players’ body size (stature and body mass) and physical characteristics (upper-body absolute strength, upper-body muscular endurance, sprint time, and aerobic endurance). All the testing occurred indoors at the Sports Science Institute of South Africa (SSISA) under the supervision of a strength and conditioning specialist well trained in the testing protocol and procedures. He was present at SSISA for the duration of the study and maintained continuity in the testing procedures. All tests were conducted in 1 day and standardized warm-ups were conducted before each session. Data for the multistage shuttle run test (MSSRT) and 10-m sprint times were not collected in 2008, 2010, and 2000, respectively. The testing protocol was conducted as follows. Body Mass
Each player was weighed on an electronic scale (SECA, California, USA, MVW Industrial Floor scale; 200 kg capacity) while barefoot and wearing only shorts and a tshirt. Body mass was recorded in kilograms (kg) to the nearest 100 g (0.1 kg) (technical error of measurement [TEM] = 0.48 kg, 95% confidence interval [CI] = 0.33–0.83 kg; TEM as % coefficient of variation [CV] = 0.6%, 95% CI = 0.4–0.7%) (data of High Performance Centre [HPC]). Stature
The measurement was recorded with the subject barefoot with his arms hanging by his sides. His heels, buttocks, upper back, and head were in contact with the stadiometer (SECA, California, USA, SECA Leceister 214 stadiometer). VOLUME 29 | NUMBER 4 | APRIL 2015 |
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Changes in Body Size and Physical Characteristics
Figure 1. Comparison graphs between forwards and backs for changes over time for stature, body mass, bench press (absolute and relative) during the 13year period of the study. Data are shown as mean 6 95% CI. CI = confidence interval.
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Figure 2. Comparison graphs between forwards and backs for changes over time for pull-ups, MSSRT, and sprint times (10 and 40 m) during the 13-year period of the study. Data are shown as mean 6 95% CI. MSSRT = multistage shuttle run test; CI = confidence interval.
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Changes in Body Size and Physical Characteristics movements of the upper torso and a set of 5–10 repetitions at 40–50% of their estimated 1RM. The weight was then increased to 60–70% of predicted 1RM and 3 repetitions were completed. Subjects rested for 5 minutes before the weight was increased to the estimated 1RM. If the subject completed the repetition successfully, the weight was increased by 5–10%. If the attempt was unsuccessful, the weight was decreased by 2.5–5%. The next repetition was only attempted after a 4-minute rest period. The maximum weight lifted was recorded as the player’s 1RM. The tester provided verbal encouragement throughout the lift. An attempt was deemed correct if the player lifted the bar in a controlled manner and lowered the bar to the center of his chest (lightly touching the chest), followed by extending the arms into a fully extended position. The attempted lift was disqualified if the player lifted his buttocks off the bench during the movement, if he bounced the bar off his chest, or if the spotter was required to assist in the lift. The 1RM bench Figure 3. Percentage change for both groups combined over the 13-year period of the study (percentages calculated so that a faster sprint time is expressed as a positive change). The variation around each data point press test is a reliable (intraclass represents the 95% CI. CI = confidence interval. correlation coefficient [ICC], R = 0.99; CV = 1.4%) and valid test of upper-body strength (24). Once the 1RM score had been determined, a relative bench The measurement was recorded as the height from the press score was calculated by dividing the 1RM (kg) score by floor to the vertex of the head. The measurement was the body mass (kg). recorded at the point of deep inhalation to the nearest millimeter (TEM = 0.33 cm, 95% CI = 0.26–0.44 cm; TEM Muscular Endurance (Pull-ups) as % CV = 0.2%, 95% CI = 0.2–0.3%) (HPC data). The test was conducted with an underhand grip and the hands 10–15 cm apart. The player started in the hanging Muscular Strength (Bench Press) position and ascended to a position with his chin above The 1 repetition maximum (1RM) bench press test was used the bar. When returning to the starting position, the arms to evaluate the player’s maximal upper-body strength. The needed to be in the fully extended position. The maximal test was conducted according the National Strength and number of completed pull-ups was recorded. Gabbett et al. Conditioning Association 1RM testing protocol (3). Accord(14) showed a TEM for pull-ups to be 7.3% and the ICC ing to this protocol, players were supine on a bench in the 5being R = 0.94. point contact position, with their feet flat on the floor and Ten- and Forty-Meter Sprint Times their hips and shoulders in contact with the bench. The The warm-up supervised by a strength and conditioning players were instructed to grip the bar so that the distance specialist consisted of 5 minutes of submaximal cycling, between their hands was just more than the shoulder width. followed by light jogging with dynamic warm-ups and All players completed a light warm-up including dynamic
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Journal of Strength and Conditioning Research movement preparation of all major leg musculature. Players then performed 2 trial runs on the synthetic rubber surface for 40 m at 65% of the maximal effort and then again to the 10-m mark at 80% of the maximal effort. Subjects were then given 5 minutes to do additional stretching of their choice. The photoelectric sensors (Brower Speed Trap II wireless sprint system; Brower Timing Systems, Draper, UT, USA) were placed at the start line and at distances of 10 and 40 m from the start. Players were instructed to sprint maximally from a sprinter start position, for 40 m through the sensors. Each subject completed 2 maximal effort runs separated by a 5-minute recovery period. Times were automatically recorded at 10- and 40-m sprint times, respectively. The fastest time for each distance was recorded for analysis. Gabbett (13) showed test-retest reliability of the 10- and 40-m sprint to be R = 0.88 and 0.92, respectively, with a TEM of 2.07 and 1.25%, respectively. Aerobic Capacity (Multistage Shuttle Run Test)
Subjects were instructed to run the MSSRT according to the pace determined by the recorded sound (22). The test started at a slow speed that increased each minute as the players ran laps between 2 lines 20 m apart. If the player failed to keep up with the recorded sound for 2 consecutive laps, he was withdrawn from the test. The player could however voluntarily withdraw if he felt he was unable to maintain the pace set by the recorded sound. The score for this test was defined as the number of successfully completed laps of 20 m. Leger et al. (22) showed test-retest reliability to be R = 0.89 and R = 0.95, with a TEM of 12.1%. Statistical Analyses
Data were processed using Statistica version 10 (StatsSoft Inc., Tulsa, OK). In 2008, testing did not occur in January or December; therefore, these data are excluded from the analysis. Descriptive statistics were used to analyze the data for each “year” (1998–2010) and position (forwards and backs). Data are represented as mean 6 95% CI in the figures and mean 6 SD in the text. A Levene’s test of homogeneity was used to determine whether the variance was equal for each variable. A 2-way analysis of variance was used to determine whether there were significant differences for either main effect of “year” or “position” or for the interaction between “year 3 position.” If the main effect of “year” or interaction (year 3 position) was significant, a Tukey post hoc test was used to identify specific differences. Statistical significance was accepted when p # 0.05. The Cohen’s effect size (ES) was calculated to quantify the magnitude of difference between groups and subgroups using the nomenclature categorization of ES according to 0.2 (small), 0.5 (medium), and 0.8 (large) (6). The TEM for HPC data was determined using the spreadsheet “Reliability from consecutive pairs of trials,” downloaded from www.sportsci.org (19). The differences between the forwards and backs have been summarized, by expressing
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the differences between each variable tested as a percentage using the following formula:
ðForwards2BacksÞ=ð½Forwards þ Backs=2Þ3100: RESULTS Stature
The forwards (mean: 181 6 8 cm in 2001 to 188 6 8 cm in 2009) were taller than the backs (mean: 172 6 5 cm in 1998 to 182 6 5 cm in 2007) (p = 0.0001). The stature for all groups (i.e., forwards and back combined) increased slightly over the duration of the study (mean: 179 6 9 cm in 1998 to 184 6 7 cm in 2010) (Figure 1A). Body Mass
The forwards were consistently heavier (mean: 99 6 9 kg in 1998 to 108 6 7 kg in 2009) than the backs (mean: 74 6 10 kg in 1998 to 88 6 8 kg in 2007) (p = 0.0001). The body mass of both the forwards and backs combined increased significantly over the study (p = 0.0001) (Figure 1B). The ES between the body mass in 1998 (87 6 16 kg) and 2010 (99 6 13 kg) was ES = 0.80. Bench Press
Figure 1C shows that the absolute strength scores (1RM bench press) for the whole group increased by over 40% from 1998 to 2010 (89 6 18 vs. 135 6 22 kg; p , 0.0001; ES = 1.63). The forwards increased by 32% from 1998 to 2010 (99 6 14 kg vs. 138 6 23 kg), whereas the backs increased by 51% (77 6 15 kg to 130 6 20 kg) over the same period. Both groups increased at the same rate (i.e., the interaction between “position” and “year” was not significant [p = 0.37]). Relative Bench Press
The relative bench press score for both groups combined between 1998 and 2010 increased (p = 0.0001) (ES = 0.58) (Figure 1D). The difference between the scores in 1998 vs. 2010 had an ES = 0.58. The mean scores of the forwards over this time period ranged from 1.0 to 1.3 kg per kilogram body weight, which was slightly less than the mean score of the backs (mean range: 1.0–1.5 kg per kilogram body weight) (p = 0.001). There was no significant interaction between “position” 3 “year” (p = 0.095). Pull-ups
The number of pull-ups was different between position (14 6 6 vs. 11 6 4 repetitions; backs vs. forwards) (p = 0.0001) (Figure 2E). Also, the number of pull-ups for the group increased from 10 6 4 repetitions in 1998 to 15 6 6 repetitions in 2010 (p = 0.0001) (ES = 0.83). There was no interaction between “position” 3 “year” (p = 0.12). Multistage Shuttle Run Test
The backline players completed on average more shuttles (mean: 101 6 13 shuttles in 1998 to 102 6 12 shuttles in VOLUME 29 | NUMBER 4 | APRIL 2015 |
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Changes in Body Size and Physical Characteristics 2010) than their forward counterparts (mean: 88 6 16 shuttles in 1998 to 86 6 15 shuttles in 2010) (p = 0.0001) (Figure 2F). There was no change over the study for the combined group (p = 0.929), and there was no interaction between “position” 3 “year.” Ten- and Forty-Meter Sprint Times
The 10-m sprint times for the combined group mean ranged from 1.86 6 0.10 seconds in 1998 to 1.73 6 0.10 seconds in 2010 (Figure 2G). The backs were consistently faster than the forwards in each year over the duration of the study for 10 m (p = 0.0001). There was a significant interaction (position 3 year) for 10 m (p = 0.021). The sprint times of the forwards decreased each year after 4 years (i.e., from 2001) (2001 vs. 2010; ES = 1.36), whereas the backs decreased from 1998 to 2003 and then decreased each year thereafter (ES z 1.1 for each year compared with 1998). The 40-m sprint time for the combined group ranged from 5.44 6 0.20 seconds in 1998 to 5.23 6 0.30 seconds in 2010 (Figure 2H). The backs were faster than the forwards (p = 0.0001). Both groups got faster over the study in the 40 m (1998 vs. 2010; ES = 0.61) (p = 0.0001). There was no significant interaction (position 3 year) for 40 m (Figure 3). Summary of Position Differences
Backs were superior compared with forwards in the following tests: Pull-ups: 24% greater number of pull-up repetitions Relative bench press: 10% greater in strength to body weight measure 40-m sprint time: 5% faster time recorded over 40 m 10-m sprint time: 3% faster time recorder over 10 m MSSRT: 11% greater number of 20-m shuttles run. Summary of Changes Over Time
Forwards were superior compared with the backs in the following characteristics: Stature: 5% taller (cm) Body mass: 23% heavier (kg) Absolute bench press: 18% more mass lifted in 1 repetition bench press (kg).
DISCUSSION The aim of this study was to determine whether there were changes in body size and physical characteristics of South African under-20 rugby union players over a 13-year period. The main finding of this study was that the players got heavier, slightly taller, stronger, and faster with better local muscle endurance over the 13 years of this study. Body mass of players competing in collision sports is an important characteristic associated with performance (30). This is supported by a recent study that showed a significant correlation between body mass and performance in rugby (30). In addition, evidence suggests that over the past 37 years, there has been a general increase in the overall body mass of all rugby players (25,26,30). The practical significance of these
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findings is that the coaches and strength and conditioning specialists have evidence that there is a trend for the players getting bigger and stronger. This highlights the importance of strength training, especially hypertrophy-type training during the off season. It was not surprising that the forwards were about 4.7% taller than the backline players because certain positions are dependent on the players being tall in rugby union. For example, players in the lock position (a forward) are required to jump in the line out to retrieve the ball, and it is generally advantageous that they are the tallest players in the team (8). The fact that stature only changed slightly over the 13 years of the study, in contrast to body mass, can perhaps be explained because stature is 80% inheritable and the remaining 20% can be attributed to various factors such as the environment, nutrition, and training (34). In contrast, body mass has the capacity to change significantly in a short period. For example, a 4-year study on male college students showed that body mass increased or decreased by between 8.7 and 16.8 kg during this time (16). Also in sports defined by weight categories, it is common for body mass to decrease before competition and then increase significantly after competition (4). The finding of stature changing in this study is similar to the findings of a study on English professional players who showed similar trends over a 10-year period (2002–2011) (12). Although it was not measured in this study, it can be speculated that the increases in body mass over time can be attributed to the changing demands of the game (28), training (15), and nutritional intervention (33). Drugs, in particular anabolic steroids, have also been attributed to the increases in body mass (18). However, there is random testing for drugs in rugby, with a low rate of positive tests (32); therefore, it is unlikely that this is the main reason for the increase in body mass. An alternative explanation is that the transition into the professional era has increased the players’ awareness about good nutrition and year round strength training leading to the increase in body mass and overall physicality. The next finding was that players got stronger throughout the 13 years of the study. Absolute strength is an important attribute for performance in rugby regardless of playing position (12). However, certain positions require a greater absolute strength than other positions because of the specific demands of that particular position. Muscular strength, measured in the laboratory, has a strong relationship to on-field performance in contact sports and more specifically rugby (5,31). In particular, absolute strength is related to the number of turnovers in a match (31). It is therefore not surprising that the forwards were 18% stronger than the backs. This once again places a significant emphasis on the importance of strength training in collision sports such as rugby. Not only will it allow players to withstand the demands of the game but also reduce the risk of sustain injury and prolong their careers.
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Journal of Strength and Conditioning Research Over the 13 years of the study, the number of pull-ups improved by almost 50%. Pull-ups measure the ability to repeat muscle contractions, when performed unweighted, for as many repetitions as possible with no time constraints. Rugby players are expected to produce repeated muscle contractions over the duration of a match without showing signs of fatigue, which may impair performance. In particular, a team is expected to make about 100 tackles per match (11) with forwards making the majority of these contacts (35). Players are also expected to perform optimally at rucks and mauls as well as being competitive in the line outs by efficient lifting of the jumpers (15). Players who are more “fatigue resistant” have a distinct advantage over players who show symptoms of fatigue during a match. Although the pull-up results showed that the forwards were less fatigue resistant compared with the backs, they were also heavier, which would have been a handicap, as heavier players have more mass to lift. Although the measurement might be criticized for not being specific (1 minute for the test vs. 80 minutes for the match), it has been shown that there is a significant but low correlation between pull-ups and the ability to turnover the ball during a match (31). It may be argued that the significant increase in upper-body muscular endurance, as shown by the increase in pull-ups over the 13year period, has contributed to this skill during a game. This finding is in contrast to the overall aerobic capacity, which did not change. The lack of change in aerobic capacity can be interpreted in 2 ways. First, this may be a consequence of players getting heavier or second the level of aerobic capacity, which has persisted for 13 years, meets the demands of the game, and the characteristics of the players have evolved in a direction, which provides a competitive advantage (i.e., mass, strength, local muscle endurance, and sprinting speed). When considering sprint times, performance in the 10 m represents acceleration, whereas performance in the 40 m represents top-end speed (10). As expected, the backs were faster than the forwards for 10 and 40 m (7,9). In both these tests, forwards and backs showed marginal improvements despite the increase in body mass. The backs improved earlier in the study for the 10 m compared with the forwards, whereas the rate of increase for the 40 m was similar. This may be attributed to the fact that the body mass of the forwards increased at a quicker rate than the backs, leading to a slower increase in sprint times because of an increase in total body mass. There is a small inverse association between 10 m times and the number of line breaks, tackle breaks, meters advanced, and tries scored during a match (31). In conclusion, the players became heavier, stronger, taller, and improved their upper-body muscular endurance over the 13 years of the study. Furthermore, sprint times over 10 and 40 m improved over the same time period despite the increase in body mass, whereas aerobic capacity remained unchanged. Overall, it can be speculated that these changes are the result of physical training and nutrition, but it could also be influenced by pressure to select players with the
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physical characteristics associated with success in the game. The demands of the game have also changed as a result of the rule changes. With the increase in physical demands, players have been spending more time on strength and conditioning ensuring that they are in “peak” physical condition to match the demands imposed on them.
PRACTICAL APPLICATIONS There is pressure to select bigger, stronger, and faster players in higher-level rugby teams, as these characteristics have been associated with superior performance. The changes in body mass, strength, and speed observed in these under-20 players may be ascribed to training and nutrition. This study emphasizes the importance of strength and conditioning prescription for all rugby players to enable them to gain a physical advantage over their opponents. For the effects to be evident at the under-20 level, the players need to start specific training for this when they are younger. These young players need to ensure that they spend quality time on strength and conditioning, specific to their position, as part of their overall preparation for rugby, particularly if they want to gain a physical advantage over the players in the opposing team as they grow and mature. Therefore, it is important that strength and conditioning professionals who are involved in collision sports understand the importance that size and strength and power in these sporting codes and implement strategies in their programming to address these to characteristics. Further to this, it was evident that aerobic capacity, as measured by the MSSRT, remained unchanged over the period of the study. This could be an indication that it is an area that requires more attention in future strength and conditioning programs in rugby union, providing mass, strength, and speed are not compromised.
REFERENCES 1. Anzell, AR, Potteiger, JA, Kraemer, WJ, and Otieno, S. Changes in height, body weight and body composition in American football players from 1942 to 2011. J Strength Cond Res 27: 1–8, 2013. 2. Argus, CK, Gill, ND, and Keogh, JW. Characterization of the differences in strength and power between different levels of competition in rugby union athletes. J Strength Cond Res 26: 2698–2704, 2012. 3. Baechle, TR and Earle, RW. Essentials of Strength Training and Conditioning (3rd ed.). Colorado Springs, CO: Human Kinetics, 2008. 4. Burke, L. Food for Sports Performance (2nd ed.). Allen & Unwin, Australia, 1995. 5. Burr, JF, Jamnik, RK, Baker, J, Macpherson, A, Gledhill, N, and McGuire, EJ. Relationship of physical fitness test results and hockey playing potential in elite level ice hockey players. J Strength Cond Res 22: 1535–1543, 2008. 6. Cohen, J. Statistical Power Analysis for the Behavioral Sciences (2nd ed.). Lawrence Erlbaum, New York, 1998. 7. Cunniffe, B, Proctor, W, Baker, JS, and Davies, B. An evaluation of the physiological demands of elite rugby union using global positioning system tracking software. J Strength Cond Res 23: 1195– 1203, 2009. 8. Durandt, J, Toit Du, S, Borresen, J, Hew-Butler, T, Masimla, H, Jakoet, I, and Lambert, M. Fitness and body composition profiling of elite junior South African rugby players. S Afr J Sports Med 18: 38–45, 2009. VOLUME 29 | NUMBER 4 | APRIL 2015 |
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Changes in Body Size and Physical Characteristics 9. Duthie, G, Pyne, D, and Hooper, S. Applied physiology and game analysis of rugby union. Sports Med 33: 973–991, 2003. 10. Duthie, GM, Pyne, D, Marsh, DJ, and Hooper, SL. Sprint patterns in rugby union players during competition. J Strength Cond Res 20: 208–214, 2006. 11. Fuller, CW, Brooks, JHM, Cancea, RJ, Hall, J, and Kemp, SPT. Contact events in rugby union and their propensity to cause injury. Br J Sports Med 41: 862–867, 2007. 12. Fuller, CW, Taylor, AE, Brooks, JHM, and Kemp, SPT. Changes in the stature, body mass and age of English professional rugby players: A 10-year review. J Sports Sci 31: 795–802, 2013. 13. Gabbett, TJ. Physiological characteristics of junior and senior rugby league players. Br J Sports Med 36: 334–339, 2002. 14. Gabbett, TJ, Johns, J, and Riemann, M. Performance changes following training in junior rugby league players. J Strength Cond Res 23: 961–976, 2008. 15. Gamble, P. Physical preparation for elite-level rugby union football. Strength Cond J 26: 10–23, 2004. 16. Gropper, SS, Simmons, KP, Connell, LJ, and Ulrich, PV. Changes in body weight, composition and shape: A 4-year study of college students. Appl Physiol Nutr Metab 37: 1118–1123, 2012. 17. Hauspie, RC, Vercauteren, M, and Susanne, C. Secular changes in growth and maturation: An Update. Acta Paediatr 7: 20–27, 1997. 18. Hoffman, JR, Faigenbaum, AD, Ratamess, NA, Ross, R, Kang, J, and Tenenbaum, G. Nutritional supplementation and anabolic steroid use in adolescents. Med Sci Sports Exerc 40: 15– 24, 2008. 19. Hopkins, WG, ed. Sportsci [Online] (2012 ed.). Available at: http:// www.sportsci.org. Accessed 2014.
23. Lidor, R, Coˆte´, J, and Hackfort, D. ISSP position stand: To test or not to test? the use of physical skill tests in talent detection and in early phases of sport development. Int J Sport Excer Psychol 7: 131– 146, 2009. 24. McCurdy, K, Langford, G, Jenkerson, D, and Doscher, M. The validity and reliability of the 1RM bench press using chain-loaded resistance. J Strength Cond Res 22:678–683, 2008. 25. Norton, K and Olds, T. Morphological evolution of athletes over the 20th century. Sports Med 31: 763–783, 2001. 26. Olds, T. The evolution of physique in male rugby union players in the twentieth century. J Sports Sci 19: 253–262, 2001. 27. Parker, Z. Factors Associated with Success in South African Rugby Union: Faculty of Health Sciences, University of Cape Town, South Africa, 2013. pp. 1–63. 28. Quarrie, KL and Hopkins, WG. Changes in player characteristics and match activities in Bledisloe Cup rugby union from 1972 to 2004. J Sports Sci 25: 895–903, 2007. 29. Sedeauda, A, Marc, A, Schipman, J, Schaal, K, Danial, M, Guillaume, M, Berthelot, G, and Toussaint, JF. Secular trend: morphology and performance. J Sports Sci 32: 1146–1154, 2014. 30. Sedeaud, A, Marc, A, Schipman, J, Tafflet, M, Hager, JP, and Toussaint, JF. How they won Rugby World Cup through height, mass and collective experience. Br J Sports Med 46: 580–584, 2012. 31. Smart, D, Hopkins, WG, Quarrie, KL, and Gill, N. The relationship between physical fitness and game behaviours in rugby union players. Eur J Sport Sci: 14 Suppl 1: S8–S17, 2014. 32. South African Institute of Drug Free Sport. Available at: http:// www.drugfreesport.org.za/. Accessed 2013.
20. International Rugby Board. Available at: http://www.irb.com/jwc/. Accessed 2013.
33. Tarnopolsky, MA. Building muscle: Nutrition to maximize bulk and strength adaptations to resistance exercise training. Eur J Sport Sci 8: 67–76, 2008.
21. Lacome, M, Piscione, J, Hager, J-P, and Bourdin, M. A new approach to quantifying physical demand in rugby union. J Sports Sci: 32: 290–300, 2014.
34. Tucker, R and Collins, M. What makes champions? A review of the relative contribution of genes and training to sporting success. Br J Sport Med 46: 555–561, 2012.
22. Leger, LA, Mercier, D, Gadoury, C, and Lambert, J. The multistage 20 metre shuttle run test for aerobic fitness. J Sports Sci: 6: 93–101, 1988.
35. van Rooyen, M, Rock, K, Prim, S, and Lambert, M. The quantification of contacts with impact during professional rugby matches. Int J Perform Anal Sport 8: 113–126, 2008.
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Sports Science Institute of South Africa, Discovery High Performance Center; 2Department of Human Biology, Exercise Science and Sports Medicine, Faculty of Health Sciences, University of Cape Town; and 3South African Rugby Union ABSTRACT
INTRODUCTION
Lombard, WP, Durandt, JJ, Masimla, H, Green, M, and Lambert, MI. Changes in body size and physical characteristics of South African under-20 rugby union players over a 13-year period. J Strength Cond Res 29(4): 980–988, 2015—This study compared changes in the body size and physical characteristics of South African under-20 rugby union players over a 13-year period. A total of 453 South African under-20 players (forwards: n = 256 and backs: n = 197) underwent measurements of body mass, stature, muscular strength, endurance, and 10- and 40-m sprint times. A 2-way analysis of variance was used to determine significant differences for the main effects of position (forwards vs. backs) and time (1998–2010). The pooled data showed that forwards were significantly heavier (22%), taller (5%), and stronger (18%) than the backs. However, when 1 repetition maximum strength scores were adjusted for body mass, backs were stronger per kg body mass. Stature did not change over the 13-year period for both groups. There were, however, significant increases in muscular strength (50%), body mass (20%), and muscular endurance (50%). Furthermore, an improvement in sprint times over 40 (4%) and 10 m (7%) was evident over the period of the study. In conclusion, the players became heavier, stronger, taller, and improved their upperbody muscular endurance over the 13 years of the study. Furthermore, sprint times over 10 and 40 m improved over the same time period despite the increase in body mass. It can be speculated that the changes in physical characteristics of the players over time are possibly a consequence of (a) adaptations to the changing demands of the game and (b) advancements in training methods.
KEY WORDS forwards, backs, physiological testing
Address correspondence to Wayne P. Lombard, [email protected]. 29(4)/980–988 Journal of Strength and Conditioning Research Ó 2015 National Strength and Conditioning Association
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ugby union is an intermittent high-intensity collision sport, contested between 2 teams of 15 players. There are 8 forward players (forwards) and 7 backline players (backs) in each team. The forwards, whose key responsibility is gaining possession of the ball, are generally taller and heavier than the backs (8,12). However, the backs are usually faster than the forwards and are responsible for gaining field possession and scoring points (7,28). The playing time is 80 minutes (2 halves of 40 minutes), with the time of the ball in play ranging from 35 to 45 minutes, and the rest of the time made up of stoppages (21). Modern day athletes in general are bigger, stronger, and faster, especially at the elite level compared with athletes of 20 years ago (29). This can be attributed to a refinement of training techniques (1,26), nutrition (1,18), and in some cases ergogenic aids (17,18,26). In rugby union, the average size of players has steadily increased from 1905 with the rate of change from 1975 to 1999 being almost 3–4 times greater than the rate of change between 1905 and 1974 (26). This may also have something to do with the changing demands of the game, which have occurred as a result of certain rule changes (9). The number of collisions between players during a match has also increased (35). Between 1995 and 2004, the ball-in-play time increased by nearly 6 minutes in Bledisloe Cup matches, and the number of rucks increased from an average of 72–178 (28). It can be argued that these rule changes have affected the physical demands of the game. It is for this reason that recent research has tried to identify the physiological demands of the modern game. For example, a study using global positioning system tracking software provided insight into the various stresses placed on different positions (7). The study showed backs spent 42% of playing time at 80–90% of maximum heart rate (HRmax), whereas forwards spent approximately 27% of playing time in this heart rate zone. The study also showed that players generally only sprinted for a maximum of 4–6 seconds at any given time, covering distances of anywhere between 30 and 60 m (7). One of the key findings of the study was the actual
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Journal of Strength and Conditioning Research number of collisions experienced by the forwards (1,274 collisions) vs. backs (798 collisions) during a match (7). About 15% of the tackles of the backs and 25% of the forwards were rated as “moderate-heavy” to “severe” (7). Another study of provincial professional players used video analysis to show that forwards were involved in 68% of the total collisions (35). Therefore, it is generally accepted that the backline players are faster, whereas the forwards have more contact and as a result are generally the bigger and stronger players to ensure that they can handle these collisions. Physiological profiling of players has become ever increasingly important to determine their readiness to withstand the demands of a high-intensity contact sport (23). Furthermore, it has been shown that there is a direct relationship between specific physical characteristics and game statistics (e.g., sprint times vs. line breaks) in rugby union (31). For example, it was shown that the bigger teams are generally the more successful teams that compete in the Rugby World Cup (29). It has been well documented that strength, power, and upper-body muscular endurance are important characteristics of modern era rugby players, allowing them to be more fatigue resistant and stronger in the tackle and ball carrying situations (2,9). With this in mind, it is plausible to assume that in the modern era of professional rugby, players who are generally bigger, faster, stronger, and can resist fatigue tend to have an advantage over smaller, less powerful, and less fit opponents (31). Indeed, at all the previous world cup tournaments, the team performing best had the tallest backs and heaviest forwards (30). Therefore, to perform at a high level and be able to cope with the physicality of the modern game, players need to train to become stronger, bigger, and faster, while being able to resist the fatigue arising from short duration high intensity activity. It is obviously also important for the players to have a high level of skill for the demands of a specific position, but it is increasingly difficult for players without these physical characteristics to successfully compete at the highest levels, even if they have the prerequisite skills. There are a lack of studies on the body size and physical characteristics of junior rugby players (under 20 years) competing at the international level. These data are important because about 32% of players who play for the South African under-20 team progress to play for the senior national team when they mature (27). Therefore, it is important to have reference data for young rugby players so that they can be adequately prepared for competition at a senior level. Moreover, quantifying how these measurements have evolved over time provides an insight into which measurements are particularly important for success. Therefore, the aim of this study was to compare changes in the body size and physical characteristics of South Africa’s National under-20 rugby union players (forwards and backs) over a 13-year period from 1998 to 2010. This period spans an era starting just after the onset of professionalism of the game to the modern era where the influence of professionalism has filtered down to junior (under-20) levels.
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METHODS Experimental Approach to the Problem
The study is a retrospective descriptive study using a repeated cross-sectional design conducted over 13 years, in which the body size and physical characteristics of under-20 rugby players were measured. Subjects
Each player completed a preparticipation screening questionnaire and an informed consent form before testing. All under 18 players had parental consent prior to participating. Players who had contraindications to testing were excluded from that particular test if necessary. The population sample consisted of under-20 rugby players who represented the junior South African National team between 1998 and 2010 (n = 453). The Human Research Ethics Committee of the University of Cape Town approved the study (HREC REF 001/2011). The group was divided into 2: forwards (n = 256) and backs (n = 197). The mean age of the players was 18.1 6 0.7 years at the time of testing. Players were tested in either December or January of 1998–2010 before the finalization of the squad before the junior world championships of that year. The championships were held in different parts of the world between the months of June and July (20). Testing Protocol
The testing protocol consisted of an evaluation of the players’ body size (stature and body mass) and physical characteristics (upper-body absolute strength, upper-body muscular endurance, sprint time, and aerobic endurance). All the testing occurred indoors at the Sports Science Institute of South Africa (SSISA) under the supervision of a strength and conditioning specialist well trained in the testing protocol and procedures. He was present at SSISA for the duration of the study and maintained continuity in the testing procedures. All tests were conducted in 1 day and standardized warm-ups were conducted before each session. Data for the multistage shuttle run test (MSSRT) and 10-m sprint times were not collected in 2008, 2010, and 2000, respectively. The testing protocol was conducted as follows. Body Mass
Each player was weighed on an electronic scale (SECA, California, USA, MVW Industrial Floor scale; 200 kg capacity) while barefoot and wearing only shorts and a tshirt. Body mass was recorded in kilograms (kg) to the nearest 100 g (0.1 kg) (technical error of measurement [TEM] = 0.48 kg, 95% confidence interval [CI] = 0.33–0.83 kg; TEM as % coefficient of variation [CV] = 0.6%, 95% CI = 0.4–0.7%) (data of High Performance Centre [HPC]). Stature
The measurement was recorded with the subject barefoot with his arms hanging by his sides. His heels, buttocks, upper back, and head were in contact with the stadiometer (SECA, California, USA, SECA Leceister 214 stadiometer). VOLUME 29 | NUMBER 4 | APRIL 2015 |
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Changes in Body Size and Physical Characteristics
Figure 1. Comparison graphs between forwards and backs for changes over time for stature, body mass, bench press (absolute and relative) during the 13year period of the study. Data are shown as mean 6 95% CI. CI = confidence interval.
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Figure 2. Comparison graphs between forwards and backs for changes over time for pull-ups, MSSRT, and sprint times (10 and 40 m) during the 13-year period of the study. Data are shown as mean 6 95% CI. MSSRT = multistage shuttle run test; CI = confidence interval.
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Changes in Body Size and Physical Characteristics movements of the upper torso and a set of 5–10 repetitions at 40–50% of their estimated 1RM. The weight was then increased to 60–70% of predicted 1RM and 3 repetitions were completed. Subjects rested for 5 minutes before the weight was increased to the estimated 1RM. If the subject completed the repetition successfully, the weight was increased by 5–10%. If the attempt was unsuccessful, the weight was decreased by 2.5–5%. The next repetition was only attempted after a 4-minute rest period. The maximum weight lifted was recorded as the player’s 1RM. The tester provided verbal encouragement throughout the lift. An attempt was deemed correct if the player lifted the bar in a controlled manner and lowered the bar to the center of his chest (lightly touching the chest), followed by extending the arms into a fully extended position. The attempted lift was disqualified if the player lifted his buttocks off the bench during the movement, if he bounced the bar off his chest, or if the spotter was required to assist in the lift. The 1RM bench Figure 3. Percentage change for both groups combined over the 13-year period of the study (percentages calculated so that a faster sprint time is expressed as a positive change). The variation around each data point press test is a reliable (intraclass represents the 95% CI. CI = confidence interval. correlation coefficient [ICC], R = 0.99; CV = 1.4%) and valid test of upper-body strength (24). Once the 1RM score had been determined, a relative bench The measurement was recorded as the height from the press score was calculated by dividing the 1RM (kg) score by floor to the vertex of the head. The measurement was the body mass (kg). recorded at the point of deep inhalation to the nearest millimeter (TEM = 0.33 cm, 95% CI = 0.26–0.44 cm; TEM Muscular Endurance (Pull-ups) as % CV = 0.2%, 95% CI = 0.2–0.3%) (HPC data). The test was conducted with an underhand grip and the hands 10–15 cm apart. The player started in the hanging Muscular Strength (Bench Press) position and ascended to a position with his chin above The 1 repetition maximum (1RM) bench press test was used the bar. When returning to the starting position, the arms to evaluate the player’s maximal upper-body strength. The needed to be in the fully extended position. The maximal test was conducted according the National Strength and number of completed pull-ups was recorded. Gabbett et al. Conditioning Association 1RM testing protocol (3). Accord(14) showed a TEM for pull-ups to be 7.3% and the ICC ing to this protocol, players were supine on a bench in the 5being R = 0.94. point contact position, with their feet flat on the floor and Ten- and Forty-Meter Sprint Times their hips and shoulders in contact with the bench. The The warm-up supervised by a strength and conditioning players were instructed to grip the bar so that the distance specialist consisted of 5 minutes of submaximal cycling, between their hands was just more than the shoulder width. followed by light jogging with dynamic warm-ups and All players completed a light warm-up including dynamic
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Journal of Strength and Conditioning Research movement preparation of all major leg musculature. Players then performed 2 trial runs on the synthetic rubber surface for 40 m at 65% of the maximal effort and then again to the 10-m mark at 80% of the maximal effort. Subjects were then given 5 minutes to do additional stretching of their choice. The photoelectric sensors (Brower Speed Trap II wireless sprint system; Brower Timing Systems, Draper, UT, USA) were placed at the start line and at distances of 10 and 40 m from the start. Players were instructed to sprint maximally from a sprinter start position, for 40 m through the sensors. Each subject completed 2 maximal effort runs separated by a 5-minute recovery period. Times were automatically recorded at 10- and 40-m sprint times, respectively. The fastest time for each distance was recorded for analysis. Gabbett (13) showed test-retest reliability of the 10- and 40-m sprint to be R = 0.88 and 0.92, respectively, with a TEM of 2.07 and 1.25%, respectively. Aerobic Capacity (Multistage Shuttle Run Test)
Subjects were instructed to run the MSSRT according to the pace determined by the recorded sound (22). The test started at a slow speed that increased each minute as the players ran laps between 2 lines 20 m apart. If the player failed to keep up with the recorded sound for 2 consecutive laps, he was withdrawn from the test. The player could however voluntarily withdraw if he felt he was unable to maintain the pace set by the recorded sound. The score for this test was defined as the number of successfully completed laps of 20 m. Leger et al. (22) showed test-retest reliability to be R = 0.89 and R = 0.95, with a TEM of 12.1%. Statistical Analyses
Data were processed using Statistica version 10 (StatsSoft Inc., Tulsa, OK). In 2008, testing did not occur in January or December; therefore, these data are excluded from the analysis. Descriptive statistics were used to analyze the data for each “year” (1998–2010) and position (forwards and backs). Data are represented as mean 6 95% CI in the figures and mean 6 SD in the text. A Levene’s test of homogeneity was used to determine whether the variance was equal for each variable. A 2-way analysis of variance was used to determine whether there were significant differences for either main effect of “year” or “position” or for the interaction between “year 3 position.” If the main effect of “year” or interaction (year 3 position) was significant, a Tukey post hoc test was used to identify specific differences. Statistical significance was accepted when p # 0.05. The Cohen’s effect size (ES) was calculated to quantify the magnitude of difference between groups and subgroups using the nomenclature categorization of ES according to 0.2 (small), 0.5 (medium), and 0.8 (large) (6). The TEM for HPC data was determined using the spreadsheet “Reliability from consecutive pairs of trials,” downloaded from www.sportsci.org (19). The differences between the forwards and backs have been summarized, by expressing
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the differences between each variable tested as a percentage using the following formula:
ðForwards2BacksÞ=ð½Forwards þ Backs=2Þ3100: RESULTS Stature
The forwards (mean: 181 6 8 cm in 2001 to 188 6 8 cm in 2009) were taller than the backs (mean: 172 6 5 cm in 1998 to 182 6 5 cm in 2007) (p = 0.0001). The stature for all groups (i.e., forwards and back combined) increased slightly over the duration of the study (mean: 179 6 9 cm in 1998 to 184 6 7 cm in 2010) (Figure 1A). Body Mass
The forwards were consistently heavier (mean: 99 6 9 kg in 1998 to 108 6 7 kg in 2009) than the backs (mean: 74 6 10 kg in 1998 to 88 6 8 kg in 2007) (p = 0.0001). The body mass of both the forwards and backs combined increased significantly over the study (p = 0.0001) (Figure 1B). The ES between the body mass in 1998 (87 6 16 kg) and 2010 (99 6 13 kg) was ES = 0.80. Bench Press
Figure 1C shows that the absolute strength scores (1RM bench press) for the whole group increased by over 40% from 1998 to 2010 (89 6 18 vs. 135 6 22 kg; p , 0.0001; ES = 1.63). The forwards increased by 32% from 1998 to 2010 (99 6 14 kg vs. 138 6 23 kg), whereas the backs increased by 51% (77 6 15 kg to 130 6 20 kg) over the same period. Both groups increased at the same rate (i.e., the interaction between “position” and “year” was not significant [p = 0.37]). Relative Bench Press
The relative bench press score for both groups combined between 1998 and 2010 increased (p = 0.0001) (ES = 0.58) (Figure 1D). The difference between the scores in 1998 vs. 2010 had an ES = 0.58. The mean scores of the forwards over this time period ranged from 1.0 to 1.3 kg per kilogram body weight, which was slightly less than the mean score of the backs (mean range: 1.0–1.5 kg per kilogram body weight) (p = 0.001). There was no significant interaction between “position” 3 “year” (p = 0.095). Pull-ups
The number of pull-ups was different between position (14 6 6 vs. 11 6 4 repetitions; backs vs. forwards) (p = 0.0001) (Figure 2E). Also, the number of pull-ups for the group increased from 10 6 4 repetitions in 1998 to 15 6 6 repetitions in 2010 (p = 0.0001) (ES = 0.83). There was no interaction between “position” 3 “year” (p = 0.12). Multistage Shuttle Run Test
The backline players completed on average more shuttles (mean: 101 6 13 shuttles in 1998 to 102 6 12 shuttles in VOLUME 29 | NUMBER 4 | APRIL 2015 |
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Changes in Body Size and Physical Characteristics 2010) than their forward counterparts (mean: 88 6 16 shuttles in 1998 to 86 6 15 shuttles in 2010) (p = 0.0001) (Figure 2F). There was no change over the study for the combined group (p = 0.929), and there was no interaction between “position” 3 “year.” Ten- and Forty-Meter Sprint Times
The 10-m sprint times for the combined group mean ranged from 1.86 6 0.10 seconds in 1998 to 1.73 6 0.10 seconds in 2010 (Figure 2G). The backs were consistently faster than the forwards in each year over the duration of the study for 10 m (p = 0.0001). There was a significant interaction (position 3 year) for 10 m (p = 0.021). The sprint times of the forwards decreased each year after 4 years (i.e., from 2001) (2001 vs. 2010; ES = 1.36), whereas the backs decreased from 1998 to 2003 and then decreased each year thereafter (ES z 1.1 for each year compared with 1998). The 40-m sprint time for the combined group ranged from 5.44 6 0.20 seconds in 1998 to 5.23 6 0.30 seconds in 2010 (Figure 2H). The backs were faster than the forwards (p = 0.0001). Both groups got faster over the study in the 40 m (1998 vs. 2010; ES = 0.61) (p = 0.0001). There was no significant interaction (position 3 year) for 40 m (Figure 3). Summary of Position Differences
Backs were superior compared with forwards in the following tests: Pull-ups: 24% greater number of pull-up repetitions Relative bench press: 10% greater in strength to body weight measure 40-m sprint time: 5% faster time recorded over 40 m 10-m sprint time: 3% faster time recorder over 10 m MSSRT: 11% greater number of 20-m shuttles run. Summary of Changes Over Time
Forwards were superior compared with the backs in the following characteristics: Stature: 5% taller (cm) Body mass: 23% heavier (kg) Absolute bench press: 18% more mass lifted in 1 repetition bench press (kg).
DISCUSSION The aim of this study was to determine whether there were changes in body size and physical characteristics of South African under-20 rugby union players over a 13-year period. The main finding of this study was that the players got heavier, slightly taller, stronger, and faster with better local muscle endurance over the 13 years of this study. Body mass of players competing in collision sports is an important characteristic associated with performance (30). This is supported by a recent study that showed a significant correlation between body mass and performance in rugby (30). In addition, evidence suggests that over the past 37 years, there has been a general increase in the overall body mass of all rugby players (25,26,30). The practical significance of these
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findings is that the coaches and strength and conditioning specialists have evidence that there is a trend for the players getting bigger and stronger. This highlights the importance of strength training, especially hypertrophy-type training during the off season. It was not surprising that the forwards were about 4.7% taller than the backline players because certain positions are dependent on the players being tall in rugby union. For example, players in the lock position (a forward) are required to jump in the line out to retrieve the ball, and it is generally advantageous that they are the tallest players in the team (8). The fact that stature only changed slightly over the 13 years of the study, in contrast to body mass, can perhaps be explained because stature is 80% inheritable and the remaining 20% can be attributed to various factors such as the environment, nutrition, and training (34). In contrast, body mass has the capacity to change significantly in a short period. For example, a 4-year study on male college students showed that body mass increased or decreased by between 8.7 and 16.8 kg during this time (16). Also in sports defined by weight categories, it is common for body mass to decrease before competition and then increase significantly after competition (4). The finding of stature changing in this study is similar to the findings of a study on English professional players who showed similar trends over a 10-year period (2002–2011) (12). Although it was not measured in this study, it can be speculated that the increases in body mass over time can be attributed to the changing demands of the game (28), training (15), and nutritional intervention (33). Drugs, in particular anabolic steroids, have also been attributed to the increases in body mass (18). However, there is random testing for drugs in rugby, with a low rate of positive tests (32); therefore, it is unlikely that this is the main reason for the increase in body mass. An alternative explanation is that the transition into the professional era has increased the players’ awareness about good nutrition and year round strength training leading to the increase in body mass and overall physicality. The next finding was that players got stronger throughout the 13 years of the study. Absolute strength is an important attribute for performance in rugby regardless of playing position (12). However, certain positions require a greater absolute strength than other positions because of the specific demands of that particular position. Muscular strength, measured in the laboratory, has a strong relationship to on-field performance in contact sports and more specifically rugby (5,31). In particular, absolute strength is related to the number of turnovers in a match (31). It is therefore not surprising that the forwards were 18% stronger than the backs. This once again places a significant emphasis on the importance of strength training in collision sports such as rugby. Not only will it allow players to withstand the demands of the game but also reduce the risk of sustain injury and prolong their careers.
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Journal of Strength and Conditioning Research Over the 13 years of the study, the number of pull-ups improved by almost 50%. Pull-ups measure the ability to repeat muscle contractions, when performed unweighted, for as many repetitions as possible with no time constraints. Rugby players are expected to produce repeated muscle contractions over the duration of a match without showing signs of fatigue, which may impair performance. In particular, a team is expected to make about 100 tackles per match (11) with forwards making the majority of these contacts (35). Players are also expected to perform optimally at rucks and mauls as well as being competitive in the line outs by efficient lifting of the jumpers (15). Players who are more “fatigue resistant” have a distinct advantage over players who show symptoms of fatigue during a match. Although the pull-up results showed that the forwards were less fatigue resistant compared with the backs, they were also heavier, which would have been a handicap, as heavier players have more mass to lift. Although the measurement might be criticized for not being specific (1 minute for the test vs. 80 minutes for the match), it has been shown that there is a significant but low correlation between pull-ups and the ability to turnover the ball during a match (31). It may be argued that the significant increase in upper-body muscular endurance, as shown by the increase in pull-ups over the 13year period, has contributed to this skill during a game. This finding is in contrast to the overall aerobic capacity, which did not change. The lack of change in aerobic capacity can be interpreted in 2 ways. First, this may be a consequence of players getting heavier or second the level of aerobic capacity, which has persisted for 13 years, meets the demands of the game, and the characteristics of the players have evolved in a direction, which provides a competitive advantage (i.e., mass, strength, local muscle endurance, and sprinting speed). When considering sprint times, performance in the 10 m represents acceleration, whereas performance in the 40 m represents top-end speed (10). As expected, the backs were faster than the forwards for 10 and 40 m (7,9). In both these tests, forwards and backs showed marginal improvements despite the increase in body mass. The backs improved earlier in the study for the 10 m compared with the forwards, whereas the rate of increase for the 40 m was similar. This may be attributed to the fact that the body mass of the forwards increased at a quicker rate than the backs, leading to a slower increase in sprint times because of an increase in total body mass. There is a small inverse association between 10 m times and the number of line breaks, tackle breaks, meters advanced, and tries scored during a match (31). In conclusion, the players became heavier, stronger, taller, and improved their upper-body muscular endurance over the 13 years of the study. Furthermore, sprint times over 10 and 40 m improved over the same time period despite the increase in body mass, whereas aerobic capacity remained unchanged. Overall, it can be speculated that these changes are the result of physical training and nutrition, but it could also be influenced by pressure to select players with the
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physical characteristics associated with success in the game. The demands of the game have also changed as a result of the rule changes. With the increase in physical demands, players have been spending more time on strength and conditioning ensuring that they are in “peak” physical condition to match the demands imposed on them.
PRACTICAL APPLICATIONS There is pressure to select bigger, stronger, and faster players in higher-level rugby teams, as these characteristics have been associated with superior performance. The changes in body mass, strength, and speed observed in these under-20 players may be ascribed to training and nutrition. This study emphasizes the importance of strength and conditioning prescription for all rugby players to enable them to gain a physical advantage over their opponents. For the effects to be evident at the under-20 level, the players need to start specific training for this when they are younger. These young players need to ensure that they spend quality time on strength and conditioning, specific to their position, as part of their overall preparation for rugby, particularly if they want to gain a physical advantage over the players in the opposing team as they grow and mature. Therefore, it is important that strength and conditioning professionals who are involved in collision sports understand the importance that size and strength and power in these sporting codes and implement strategies in their programming to address these to characteristics. Further to this, it was evident that aerobic capacity, as measured by the MSSRT, remained unchanged over the period of the study. This could be an indication that it is an area that requires more attention in future strength and conditioning programs in rugby union, providing mass, strength, and speed are not compromised.
REFERENCES 1. Anzell, AR, Potteiger, JA, Kraemer, WJ, and Otieno, S. Changes in height, body weight and body composition in American football players from 1942 to 2011. J Strength Cond Res 27: 1–8, 2013. 2. Argus, CK, Gill, ND, and Keogh, JW. Characterization of the differences in strength and power between different levels of competition in rugby union athletes. J Strength Cond Res 26: 2698–2704, 2012. 3. Baechle, TR and Earle, RW. Essentials of Strength Training and Conditioning (3rd ed.). Colorado Springs, CO: Human Kinetics, 2008. 4. Burke, L. Food for Sports Performance (2nd ed.). Allen & Unwin, Australia, 1995. 5. Burr, JF, Jamnik, RK, Baker, J, Macpherson, A, Gledhill, N, and McGuire, EJ. Relationship of physical fitness test results and hockey playing potential in elite level ice hockey players. J Strength Cond Res 22: 1535–1543, 2008. 6. Cohen, J. Statistical Power Analysis for the Behavioral Sciences (2nd ed.). Lawrence Erlbaum, New York, 1998. 7. Cunniffe, B, Proctor, W, Baker, JS, and Davies, B. An evaluation of the physiological demands of elite rugby union using global positioning system tracking software. J Strength Cond Res 23: 1195– 1203, 2009. 8. Durandt, J, Toit Du, S, Borresen, J, Hew-Butler, T, Masimla, H, Jakoet, I, and Lambert, M. Fitness and body composition profiling of elite junior South African rugby players. S Afr J Sports Med 18: 38–45, 2009. VOLUME 29 | NUMBER 4 | APRIL 2015 |
987
Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.
Changes in Body Size and Physical Characteristics 9. Duthie, G, Pyne, D, and Hooper, S. Applied physiology and game analysis of rugby union. Sports Med 33: 973–991, 2003. 10. Duthie, GM, Pyne, D, Marsh, DJ, and Hooper, SL. Sprint patterns in rugby union players during competition. J Strength Cond Res 20: 208–214, 2006. 11. Fuller, CW, Brooks, JHM, Cancea, RJ, Hall, J, and Kemp, SPT. Contact events in rugby union and their propensity to cause injury. Br J Sports Med 41: 862–867, 2007. 12. Fuller, CW, Taylor, AE, Brooks, JHM, and Kemp, SPT. Changes in the stature, body mass and age of English professional rugby players: A 10-year review. J Sports Sci 31: 795–802, 2013. 13. Gabbett, TJ. Physiological characteristics of junior and senior rugby league players. Br J Sports Med 36: 334–339, 2002. 14. Gabbett, TJ, Johns, J, and Riemann, M. Performance changes following training in junior rugby league players. J Strength Cond Res 23: 961–976, 2008. 15. Gamble, P. Physical preparation for elite-level rugby union football. Strength Cond J 26: 10–23, 2004. 16. Gropper, SS, Simmons, KP, Connell, LJ, and Ulrich, PV. Changes in body weight, composition and shape: A 4-year study of college students. Appl Physiol Nutr Metab 37: 1118–1123, 2012. 17. Hauspie, RC, Vercauteren, M, and Susanne, C. Secular changes in growth and maturation: An Update. Acta Paediatr 7: 20–27, 1997. 18. Hoffman, JR, Faigenbaum, AD, Ratamess, NA, Ross, R, Kang, J, and Tenenbaum, G. Nutritional supplementation and anabolic steroid use in adolescents. Med Sci Sports Exerc 40: 15– 24, 2008. 19. Hopkins, WG, ed. Sportsci [Online] (2012 ed.). Available at: http:// www.sportsci.org. Accessed 2014.
23. Lidor, R, Coˆte´, J, and Hackfort, D. ISSP position stand: To test or not to test? the use of physical skill tests in talent detection and in early phases of sport development. Int J Sport Excer Psychol 7: 131– 146, 2009. 24. McCurdy, K, Langford, G, Jenkerson, D, and Doscher, M. The validity and reliability of the 1RM bench press using chain-loaded resistance. J Strength Cond Res 22:678–683, 2008. 25. Norton, K and Olds, T. Morphological evolution of athletes over the 20th century. Sports Med 31: 763–783, 2001. 26. Olds, T. The evolution of physique in male rugby union players in the twentieth century. J Sports Sci 19: 253–262, 2001. 27. Parker, Z. Factors Associated with Success in South African Rugby Union: Faculty of Health Sciences, University of Cape Town, South Africa, 2013. pp. 1–63. 28. Quarrie, KL and Hopkins, WG. Changes in player characteristics and match activities in Bledisloe Cup rugby union from 1972 to 2004. J Sports Sci 25: 895–903, 2007. 29. Sedeauda, A, Marc, A, Schipman, J, Schaal, K, Danial, M, Guillaume, M, Berthelot, G, and Toussaint, JF. Secular trend: morphology and performance. J Sports Sci 32: 1146–1154, 2014. 30. Sedeaud, A, Marc, A, Schipman, J, Tafflet, M, Hager, JP, and Toussaint, JF. How they won Rugby World Cup through height, mass and collective experience. Br J Sports Med 46: 580–584, 2012. 31. Smart, D, Hopkins, WG, Quarrie, KL, and Gill, N. The relationship between physical fitness and game behaviours in rugby union players. Eur J Sport Sci: 14 Suppl 1: S8–S17, 2014. 32. South African Institute of Drug Free Sport. Available at: http:// www.drugfreesport.org.za/. Accessed 2013.
20. International Rugby Board. Available at: http://www.irb.com/jwc/. Accessed 2013.
33. Tarnopolsky, MA. Building muscle: Nutrition to maximize bulk and strength adaptations to resistance exercise training. Eur J Sport Sci 8: 67–76, 2008.
21. Lacome, M, Piscione, J, Hager, J-P, and Bourdin, M. A new approach to quantifying physical demand in rugby union. J Sports Sci: 32: 290–300, 2014.
34. Tucker, R and Collins, M. What makes champions? A review of the relative contribution of genes and training to sporting success. Br J Sport Med 46: 555–561, 2012.
22. Leger, LA, Mercier, D, Gadoury, C, and Lambert, J. The multistage 20 metre shuttle run test for aerobic fitness. J Sports Sci: 6: 93–101, 1988.
35. van Rooyen, M, Rock, K, Prim, S, and Lambert, M. The quantification of contacts with impact during professional rugby matches. Int J Perform Anal Sport 8: 113–126, 2008.
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